1. Field of the Invention
The present invention relates to a process for purification and recovery of L-phenylalanine (hereinafter "phenylalanine") and more particularly, to a process for purification and recovery of phenylalanine from mixtures containing phenylalanine and undesired impurities, typically from microbial fermentation broths used in the microbial production of phenylalanine.
2. Description of the Prior Art
Generally, amino acids produced by a microorganism have to be recovered from fermentation broths containing inorganic salts, other amino acids, peptides, other organic compounds, cell debris, enzymes, and other proteins. Phenylalanine traditionally has been difficult to purify and recover from fermentation broths since phenylalanine is recovered from fermentation broths containing a large amount of impurities such as nutrients, peptides, organic or inorganic compounds, cell debris, enzymes, etc.
Several methods of amino acid recovery and purification have been described in the prior art.
(1) One specific method involves an ion exchange resin. The ion exchange method utilizes an anion or a cation exchange resin in a column which adsorbs the amino acid under an appropriate pH to separate it from the reaction mixture by using acid or alkalis. Such conventional methods are shown in U.S. Pat. No. 4,584,399 to Portal et al; Cogan et al., J. Sci. Food & Agri., 32, 459-66 (1981); Abe et al., Bull, Chem Soc. Jpn. 55, 687-89, (1982)0. Lutz, Br. Jirgensons, Ber., 64, 1221 (1931); D.T. Englis and H.A. Fiess, Ind. Eng. Chem., 36, 604 (1944); and C.S. Cleaver, R.A. Hardy, Jr. and H.G. Cassidy, J.Am. Chem. Soc., 67, 1343 (1945).
(2) U.S. Pat. No. 4,399,304 to Matsuishi et al. discloses a process for recovery of phenylalanine which comprises reacting phenylalanine in a fermentation broth with sulfuric acid to produce phenylalanine 1/2 sulfate 1/2 hydrate and recovering it from the fermentation broth.
(3) U.S. Pat. No. 4,621,153 to Hatch discloses a method of recovering an amino acid from a mixture by providing a source of bivalent metal ions (calcium) capable of forming a complex with the amino acid at pH 8.5-11.
However, such ion exchange methods (1) require a large amount of acids or alkalis as an eluting agent and expensive equipment for ion exchange resin towers. Such sulfate methods (2) require a strong sulfuric acid. Furthermore, it is difficult to obtain 1/2 sulfate 1/2 hydrate salt of phenylalanine. Also, such calcium salt methods (3) are provided with a final product which has impurities so that they have lower yield.